The present invention relates, in general, to electronic components and, more particularly, to electronic components capable of sensing optical signals.
Image sensor applications such as cameras, scanners, biometric systems, etc. often use solid state electronic components to detect images. Typically the electronic components include pixel cells comprising image sensing devices integrated with signal processing and control circuitry on a single semiconductor chip. Integration of the image sensing devices with the signal processing and control circuitry offers the advantage of lower cost and higher output because conventional processing technologies can be used for their manufacture.
In operation, photons from an optical signal strike the image sensing device, thereby generating electron-hole pairs. A voltage is applied to the image sensing device to remove one of the charge species, while the other charge species is stored in an image sensing area. The charge species stored in the image sensing area are then removed. The signal processing and control circuitry measures the amount of electrical charge removed from the image sensing area and converts this measurement into a value indicating the intensity of the optical signal sensed by the image sensing device. However, due to the configuration of the image sensing area, not all of the charge species stored in the image sensing area can be removed. The charge species that remains lowers the sensitivity of the of the pixel cell and results in image lag.
Accordingly, it would be advantageous to have a structure and method for increasing the amount of charge that is removed from an image sensing device. It would be of further advantage for the structure to be manufacturable using standard processing techniques.